Golf ball mold and golf ball manufacturing method

ABSTRACT

A golf ball mold that includes a mold body configured as a plurality of mold parts which have at least a parting surface that defines a parting line at a golf ball equator and removably mate to form a cavity having an inner wall with a plurality of dimple-forming protrusions thereon is provided. The golf ball mold includes a support pin which has an end face with a plurality of dimple-forming protrusions thereon and is extendable into and retractable from the cavity. The support pin extends into the cavity to support a center sphere and, when in a retracted state, the end face thereof defines a portion of the inner wall of the cavity. The end face of the support pin includes a pole of the cavity and has a peripheral edge which intersects a parallel of latitude at 10 degrees from the pole.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/977,409, filed Dec. 23, 2010, the entire contents of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a golf ball mold and a golf ballmanufacturing method which may be suitably used for molding golf ballscomposed of a core encased by a cover of one or more layer, particularlyfor forming an outermost cover layer having a plurality of dimplesformed on the surface thereof.

In recent years, there has been a strong desire for golf balls whichpossess various performance attributes, including not only distance, butalso controllability, durability and feel on impact. Satisfying all ofthese attributes with only one type of material is generally difficult.Hence, the customary practice is to provide the ball with a structure inwhich a solid core formed of rubber, resin or the like, or a wound core,is encased by a cover of one or more layer, each layer having aparticular function. In other words, efforts have been made to achieve aperformance which addresses the needs of the player, such as a desirefor distance or controllability, by adjusting the number and thicknessof the above layers, and also adjusting the formulations, etc. of thematerials making up the respective layers.

An injection-molding method is typically used to form the outermostlayer of a golf ball having such a structure. Specifically, use is madeof a method in which a core or a sphere (referred to below as a “centersphere”) composed of such a core encased by one or more intermediatelayer (a layer other than the outermost cover layer) is placed in thecavity of a given mold, and a cover-forming material is injected betweenthe center sphere and the inner wall of the cavity. In this case, whenthe outermost layer is formed, numerous dimples are formed at the sametime by numerous dimple-forming protrusions provided on the inner wallof the cavity.

Up until now, molds having the structure shown in FIG. 6 have often beenused when producing golf balls by the above process. FIG. 6, across-sectional view showing an example of a golf ball mold according tothe prior art, depicts the state prior to injection of the cover-formingmaterial into the cavity.

In FIG. 6, a conventional mold 10 includes a mold body 20 having anupper mold half 20 a and a lower mold half 20 b which split at a partingsurface that defines a parting line PL at a golf ball equator andremovably mate to form a cavity 3 having an inner wall with numerousdimple-forming protrusions thereon, and includes support pins 40, eachhaving on an end face thereof a single dimple-forming projection, whichare extendable into and retractable from the cavity 3. The support pins40 extend into the cavity 3 to support a center sphere 31 and, in theretracted state, the end faces thereof define a portion of the innerwall of the cavity 3. Moreover, although not fully shown here, thesupport pins 40 each have a circular cross-section, and a total of sixpins—three in the upper mold half 20 a and three in the lower mold half20 b—are provided so as to be spaced at given intervals at positionshaving 120 degree rotational symmetry about the pole Q as the center.

In the above mold 10, runners 50 and resin injection ports 60 havingopenings of given surface areas are formed along the parting surface ofthe mold body 20 in such a way as to inject, between the inner wall ofthe cavity 3 and the center sphere 31, a known cover-forming materialfrom a known injection molding machine (not shown). Next, together withinjection of the cover-forming material, the support pins 40 that wereextended into the cavity are retracted, after which cooling is carriedout, thereby completing formation of the cover. The dimples at thepositions of the support pins 40 are formed at this time by thedimple-forming protrusions that were formed on the end faces of thesupport pins.

However, when the center sphere 31 is placed in the above mold 10 andthe upper and lower mold halves are closed, the support pins 40 may besubjected to excessive forces, causing them to deflect or shift, as aresult of which irregular flash sometimes forms on the surface of themolded ball. When irregular flash arises on the ball's surface, uniformtrimming of the entire ball is difficult to carry out, which may lead todimple irregularity and ultimately have an adverse effect on flightsymmetry.

Moreover, because the end faces of the support pins 40 are generallyobtained by machining the end face of a cross-sectionally circularmember at an angle so as to impart a shape which defines a portion ofthe inner wall of the cavity 3 when the support pin is in a retractedstate, the dimple-forming protrusion formed there often has anelliptical shape as seen from above. Such elliptically shaped dimplesmay sometimes adversely affect the ball's appearance, and are a majorfactor in lowering the degree of freedom in dimple design and molddesign.

To address this problem, JP-A 08-323772 and U.S. Published PatentApplication No. 2009/0297653 disclose golf ball molds wherein a centersphere placed in the mold is not supported using a plurality of thinsupport pins like those shown in FIG. 6; instead, a large-diametersupport pin having on an end face thereof a plurality of dimple-formingprotrusions is provided. However, in these molds, although the stabilitywhen supporting a center sphere improves, because the diameter of thesupport pin is too large, gases tend to collect near a pole of thecavity (at the center of the end face on the support pin) duringinjection molding, which may give rise to appearance defects.

In order to resolve the above problem of appearance defects, JP-A2002-542067 (and the corresponding U.S. Pat. No. 6,129,881) and U.S.Pat. No. 7,341,687 disclose molds in which the venting of gases near thepoles of the cavity has been improved by providing a gas-venting pin inthe large-diameter support pin. However, the venting pin and the supportpin must be separately fabricated, resulting in excessive costs.

In this way, various modifications have been made to golf ball molds soas to improve the golf ball moldability, but a fundamental solution hasyet to be found for the above problems. Accordingly, for the sake aswell of further improving the golf ball moldability and the degree offreedom in dimple design and mold design, there exists a desire for anovel approach which is capable of resolving the above-describedproblems.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a golfball mold which, particularly during formation of the outermost coverlayer of a golf ball, is able to stably hold a center sphere inside thecavity and also vents gases well when the cover-forming material isinjected into the cavity, minimizing appearance defects and theformation of problematic flash, and thus enabling stable molding to becarried out without giving rise to the above-described productionproblems. A further object of the invention is to provide a method ofmanufacturing golf balls using such a mold.

To achieve the above object, the invention provides the following golfball mold and golf ball manufacturing method.

[1] A golf ball mold comprising a mold body configured as a plurality ofmold parts which have at least a parting surface that defines a partingline at a golf ball equator and removably mate to form a cavity havingan inner wall with a plurality of dimple-forming protrusions thereon,and a support pin which has an end face with a plurality ofdimple-forming protrusions thereon and is extendable into andretractable from the cavity, the support pin extending into the cavityto support a center sphere and, when in a retracted state, the end facethereof defining a portion of the inner wall of the cavity,wherein the end face of the support pin includes a pole of the cavityand has a peripheral edge which intersects a parallel of latitude at 10degrees from the pole.[2] The golf ball mold of [1], wherein the end face of the support pinhas three or more dimple-forming protrusions thereon.[3] The golf ball mold of [2], wherein the end face of the support pinhas four or more dimple-forming protrusions thereon.[4] The golf ball mold of [1], wherein the peripheral edge of the endface on the support pin intersects a parallel of latitude at 8 degreesfrom the pole.[5] A method of manufacturing a golf ball using the golf ball mold of[1], comprising the step of molding a cover by placing a center spherein a mold cavity formed by removably mating a plurality of mold partswhich have at least a parting surface that defines a parting line at agolf ball equator and supporting the center sphere with a support pinprovided in the mold, then injecting a cover-forming material betweenthe center sphere and the cavity inner wall while at the same timeretracting the support pin.

The golf ball mold of the invention, by being provided with a supportpin having a shape that satisfies certain conditions, is able to stablyhold a center sphere within the cavity. As a result, eccentricity doesnot arise, enabling a golf ball of uniform structure to be obtained, andbecause gases near the poles of the cavity vent well when thecover-forming material is injected into the cavity, appearance defectsdo not arise. In addition, irregular flash caused by the deflection orshifting of support pins that has been a concern in conventional moldsdoes not arise, as a result of which good molded pieces can be easilyand reliably obtained, thus contributing to enhanced golf ballproductivity. Also, because the shape of the support pin used in theinventive mold is not subject to dimple design constraints, the degreeof freedom in dimple design and mold design can be greatly enhanced.Furthermore, the inventive mold also has cost advantages in that thereis no need to separately manufacture the gas venting pins provided inthe large-diameter support pins that are described in the prior art.

BRIEF DESCRIPTION OF THE DIAGRAMS

FIG. 1 is a cross-sectional view of a golf ball mold according to anembodiment of the invention.

FIG. 2 is an enlarged perspective view of the vicinity of an end portionof a support pin in the golf ball mold shown in FIG. 1.

FIG. 3 is a top view of the support pin in FIG. 2, as seen from an endface side thereof.

FIG. 4 is a top view of the support pin in a golf ball mold according toanother embodiment of the invention, as seen from the end face sidethereof.

FIG. 5 is a top view of the support pin in a golf ball mold according toyet another embodiment of the invention, as seen from the end face sidethereof.

FIG. 6 is a cross-sectional view of an example of a golf ball moldaccording to the prior art.

DETAILED DESCRIPTION OF THE INVENTION

The golf ball mold of the invention is described more fully below inconjunction with the appended diagrams. The “parting line” and “partingsurface” of the mold, as used in the description below, are defined asfollows. The “parting line” is a line that serves as a reference whenthe mold splits into a plurality of parts. For example, in the case of amold that splits into two parts, the parting line refers to a line thatserves as a reference for the mating of the upper mold half with thelower mold half, and is rectilinear. The “parting surface” of the moldrefers to the area of contact when the respective mold parts that havebeen separated based on the above parting line are joined together. In acase where dimple-forming protrusions which lie across the parting lineare provided on the parting surface, the parting surface has convexfeatures due to the dimple-forming protrusions and also has concavefeatures which correspond to the convex features. In the presentinvention, the shape of the parting surface may be suitably setaccording to the mold specifications, and is not subject to anyparticular limitation.

It is sufficient for the golf ball mold of the invention to have atleast a parting surface that defines a parting line at a golf ballequator; the number of parts into which the mold splits may be suitablyset according to the mold specifications, and is not subject to anyparticular limitation. For example, when the number of parting surfacesin the mold is small, such as in a two-part mold having a single partingsurface, mold production costs and limitations on the dimpleconfiguration can be reduced. On the other hand, in cases where aplurality of parting surfaces are provided and the mold splits into alarger number of parts, the mold release properties of the moldedarticle can be improved. For the sake of simplicity, the mold used inthe description that follows is a two-part mold which splits along thegolf ball equator as the parting line.

FIG. 1 shows an embodiment of the golf ball mold according to thepresent invention.

FIG. 1 is a cross-sectional view of a golf ball mold according to oneembodiment of the invention. The mold 1 shown here includes a mold body2 configured as an upper mold half 2 a and a lower mold half 2 b whichhave a parting surface that defines a parting line PL at a golf ballequator and removably mate to form a cavity 3 having an inner wall witha plurality of dimple-forming protrusions thereon, and support pins 4which have an end face with a plurality of dimple-forming protrusionsthereon and are extendable into and retractable from the cavity 3. Inaddition, runners 5 and resin-injection ports 6 having openings of givesurface areas are formed along the parting surface of the mold body 2 insuch a way as to inject, between the inner wall of the cavity 3 and thecenter sphere 31, a known cover-forming material from a known injectionmolding machine (not shown). When the cover-forming material isinjected, gases within the cavity 3 are released to the exterior throughgaps between the mold body 2 and the support pins 4.

In FIG. 1, the support pins 4 extend into the cavity 3 to support thecenter sphere 31 and, when in a retracted state after injection of thecover-forming material, the end faces thereof define a portion of theinner wall of the cavity 3. Moreover, these support pins 4 differ inshape from the conventionally used large-diameter support pins in that aplurality of dimple-forming protrusions are provided on the end facesthereof, and also satisfy the subsequently described conditions. Supportpin 4 shapes which may be employed in the golf ball mold 1 of theinvention are described in detail below while providing specificexamples.

FIGS. 2 and 3 show an example of a support pin 4 shape which satisfiesthe conditions of the invention. FIG. 2 is an enlarged perspective viewof the vicinity of an end portion of a support pin 4, and FIG. 3 is atop view of the support pin 4 shown in FIG. 2, as seen from an end faceside thereof. In FIG. 3, Q represents a pole of the cavity 3, and thecircles L1 and L2 drawn with dashed lines indicate the parallels oflatitude at, respectively, 10 degrees and 8 degrees from the pole Q.

The support pin 4 has, transferred to the end face thereof, four dimpleswhich have been set on the golf ball surface so as to correspond to theposition where the support pin is disposed. The end face has a shape inwhich three dimple-forming protrusions 41 b are arranged in the form ofan equilateral triangle having arcuate vertices that follow the marginsof the dimple-forming protrusions 41 b, with one more dimple-formingprotrusion 41 a being situated at a center portion of this equilateraltriangle, and which curves arcuately inward along the margins ofdimple-forming protrusions 41′ on the mold body 2 adjoining the threesides of the equilateral triangle. A land region 42 (a regioncorresponding to, on the surface of the molded ball, lands where dimplesare not formed) of a given width is provided between a peripheral edgeof the end face and each of the above dimple-forming protrusions 41 aand 41 b, so as to give a state in which the four dimple-formingprotrusions 41 a and 41 b are completely included on the end face. Here,the shape of the support pin 4 may be suitably set according to thedimple design, and is not subject to any particular limitation. However,from the standpoint of stably supporting the center sphere duringmolding, it is preferable for the shape to have symmetry, with a shapein which the dimple-forming protrusions are arranged so as to havelinear symmetry or rotational symmetry overall being especiallypreferred. Moreover, in FIGS. 2 and 3, the dimple-forming protrusions 41a and 41 b are all circular as seen from above, and have diameters ofabout 4 mm (the size at which 4 mm diameter dimples form on the surfaceof the golf ball).

From the standpoint of stably supporting the center sphere 31, it iscritical for the support pin 4 to include a pole Q of the cavity.Preferably, it is recommended that the pole Q be made to coincide withthe center of the end face on the support pin 4. If the end face of thesupport pin 4 does not satisfy the above conditions, it may be difficultto stably support the center sphere 31. In the example shown in FIGS. 2and 3, the center of the end face on the support pin 4 and the center ofthe dimple-forming protrusion 41 a coincide with the pole Q.

Next, it is critical for the peripheral edge of the end face on thesupport pin 4 to intersect a parallel of latitude L1 at 10 degrees fromthe pole Q, and it is recommended that it preferably intersect aparallel of latitude L2 at 8 degrees from the pole Q. The latitude lowerlimit, although not subject to any particular limitation, may be set toa parallel of latitude at 0.5 degree from the pole Q (not shown). Incases where the above condition is not satisfied, gases near the pole Qhave difficulty venting during molding, which may result in appearancedefects. In the example shown in FIGS. 2 and 3, the peripheral edge ofthe end face on the support pin 4 curves deeply inward toward the poleQ, intersecting with the parallels of latitude at 10 degrees and 8degrees. As a result, gases vent well near the pole Q.

At the same time, although not subject to any particular limitation, itis recommended that the peripheral edge of the end face on the supportpin 4 preferably not exceed the parallel of latitude at 40 degrees fromthe pole Q, more preferably not exceed the parallel of latitude at 35degrees, and even more preferably not exceed the parallel of latitude at30 degrees (these parallels of latitude are not shown in the diagrams).In cases where the peripheral edge of the end face on the support pin 4exceeds the above parallel of latitude, because the diameter of thesupport pin 4 becomes too large, the material may not spread entirelythroughout the space that arises from retraction of the support pin 4during molding, as a result of which poor filling may occur. Here,although not illustrated in the diagrams, the outermost portion of theperipheral edge of the support pin 4 shown in FIGS. 2 and 3 coincideswith the parallel of latitude at 17.8 degrees from the pole Q (notshown).

The width of the above land region 42 is not subject to any particularlimitation, and may be suitably set in accordance with, for example, thedimple design and the mold design. That is, where necessary, places maybe provided where the peripheral edge of the end face coincides with themargins of the dimple-forming protrusions.

The number of dimple-forming protrusions formed on the end face of thesupport pin 4 may be suitably set according to, for example, the dimpledesign and the mold specifications, and is not subject to any particularlimitation. However, from the standpoint of the stability when holdingthe center sphere, it is recommended that the number of dimple-formingprotrusions provided on the end face be preferably three or more, andespecially four or more. The upper limit in the number of dimple-formingprotrusions provided on the end face, although not subject to anyparticular limitation, is preferably not more than twenty, morepreferably not more than ten, and even more preferably not more thanseven. When the number of dimple-forming protrusions provided on the endface of the support pin 4 is too high, because the diameter of thesupport pin 4 becomes too large, the material may not spread entirelythroughout the space that arises from retraction of the support pin 4during molding, as a result of which poor filling may occur.

The gap between the support pin 4 and the upper mold half 2 a or thelower mold half 2 b, although not subject to any particular limitation,is typically set in a range where the support pin 4 slides smoothlyduring molding, flash formation can be held to a minimum, and gaseswithin the cavity 3 can be rapidly released to the exterior. A gapwithin a range of from 5 to 50 μm is preferred. If the gap is too large,the flash becomes large. On the other hand, if the gap is too small,gases within the cavity 3 are not easily vented, which may lead toappearance defects. In FIGS. 2 and 3, the above gap is set to 25 μm.

Another example of a support pin shape which satisfies the conditions ofthe invention is shown in FIG. 4.

FIG. 4 is a top view of the support pin as seen from the end face sidethereof. In FIG. 4, as mentioned above, the symbol Q represents the poleof the cavity 3, and circles L1 and L2 drawn with dashed lines representthe parallels of latitude at, respectively, 10 degrees and 8 degreesfrom the pole Q.

This support pin 4 has a shape wherein circular areas which includedimple-forming protrusions 41 c have been added outside of thedimple-forming protrusions 41 b on the support pin 4 shown in FIGS. 2and 3, thereby providing a shape having a total of seven dimple-formingprotrusions on the end face. This support pin too has, transferred tothe end face thereof, seven dimples which have been set on the golf ballsurface so as to correspond to the position where the support pin isdisposed. Moreover, as described above, because a land region 42 ofgiven width is provided between the peripheral edge of the end face andthe respective dimple-forming protrusions 41 a, 41 b and 41 c, theresult is a state wherein the seven dimple-forming protrusions 41 a, 41b and 41 c are entirely included within the end face. In this case,because the center of the end face on the support pin 4 and the centerof the dimple-forming protrusion 41 a coincide with the pole Q, and therespective dimple-forming protrusions are arranged with rotationalsymmetry overall, the center sphere 3 can be more stably held duringmolding. In addition, this peripheral edge curves deeply inward,intersecting the parallels of latitude at 10 degrees and 8 degrees fromthe pole Q, and thereby forming a shape which readily vents gases nearthe pole Q during molding. In FIG. 4, the dimple-forming protrusions 41a, 41 b and 41 c are all circular as seen from above, and have diametersof about 4 mm (the size at which 4 mm diameter dimples form on thesurface of the golf ball). The outermost portion of the peripheral edgeof the support pin 4 coincides with the parallel of latitude at 26.5degrees from the pole Q, and the gap between the support pin 4 and theupper mold half 2 a or the lower mold half 2 b is 25 μm.

FIG. 5 shows yet another example of a support pin shape which satisfiesthe conditions of the invention.

FIG. 5 is a top view of this support pin, as seen from the end face sidethereof. In FIG. 5, as mentioned above, the symbol Q represents the poleof the cavity 3, and circles L1 and L2 drawn with dashed lines representthe parallels of latitude at, respectively, 10 degrees and 8 degreesfrom the pole Q.

This support pin 4 has three dimple-forming protrusions 41 d arrangedthereon in the form of an equilateral triangle, one dimple-formingprotrusion 41 e added outside each of the three dimple-formingprotrusions 41 d, and a land region 42 of a given width provided betweenthe six dimple-forming protrusions 41 e and 41 d and the peripheral edgeof the end face. This support pin too has, transferred to the end facethereof, six dimples which have been set on the golf ball surface so asto correspond to the position where the support pin is disposed.Moreover, because a land region 42 of a given width is provided betweenthe peripheral edge of the end face and the respective dimple-formingprotrusions 41 d and 41 e, the result is a state wherein the sixdimple-forming protrusions 41 d and 41 e are entirely included withinthe end face.

The peripheral edge of the support pin 4 has a shape with curved areasthat follow the margins of each of the dimple-forming protrusions 41 dand 41 e, these curved areas, which are mutually adjoining, beingconnected by smooth curves. In particular, between the mutuallyadjoining dimple-forming protrusions 41 d, the peripheral edges curvedeeply toward the pole Q and intersect the parallels of latitude at 10degrees and 8 degrees from the pole Q. As a result, this support pin 4also has a shape that readily vents gases near the pole Q duringmolding. In this case, because the dimple-forming protrusions 41 d and41 e are arranged with rotational symmetry overall and because thecenter of the end face on the support pin 4 coincides with the center ofsymmetry for the dimple-forming protrusions 41 d and 41 e and with thepole Q, the center sphere 31 can be more stably held during molding. InFIG. 5, the dimple-forming protrusions 41 d and 41 e are all circular asseen from above, and have diameters of about 4 mm (the size at which 4mm diameter dimples form on the surface of the golf ball). Moreover, theoutermost portion of the peripheral edge of the support pin 4 coincideswith the parallel of latitude at 23.4 degrees from the pole Q, and thegap between the support pin 4 and the upper mold half 2 a or the lowermold half 2 b is 25 μm.

Because the end face of the support pin 4 can define a portion of theinner wall of the cavity 3, dimple-forming protrusions which arecircular as seen from above can easily be formed. Moreover, depending onthe dimple design, it is also possible to directly form dimple-formingprotrusions of non-circular shapes, such as polygonal, teardrop or ovalshapes, while maintaining symmetry, etc. for the ball as a whole.Accordingly, there are no constraints on dimple design, resulting in avery high degree of freedom in dimple design and mold design.

The material used in the golf ball mold of the invention may be a knownmaterial, and is not subject to any particular limitation.

When a golf ball is molded using the golf ball mold of this invention,molding may be carried out by a method and under conditions similar tothose employed when using a conventional mold. More specifically, whenthe two-part mold 1 shown in FIG. 1 is used, first, a center sphere 31is placed inside the cavity of the mold 1, and the center sphere 31 issupported by support pins 4 that have been provided in the mold 1. Next,a known cover-forming material is injected, via runners 5 and resininjecting ports 6, between the center sphere 31 and the inner wall ofthe cavity 3, along with which the support pin 4 is retracted. Coolingand solidification are then carried out, following which the upper andlower mold halves are separated and the molded article is removed. Theresulting molded article is gate cut and trimming is carried out by anordinary method to remove flash, thereby giving a golf ball having acover of one or more layer formed over a core. To enhance the design anddurability of the golf ball, the surface of the golf ball thus obtainedmay be subjected to various treatments such as stamping and painting byknown methods.

The cover-forming material used here may be a known thermoplastic resinand is not subject to any particular limitation, although preferred usemay be made of an ionomer resin or a urethane resin. The thickness ofthe cover formed may be suitably selected according to, for example, theconstruction and materials of the golf ball to be manufactured, and isnot subject to any particular limitation.

In the golf ball manufactured by the above method, the shape, number andarrangement of the dimples formed on the surface may be suitably setaccording to the ball specifications, and are not subject to anyparticular limitation. For example, the dimple shape is not limited to acircular shape, and may also be suitably selected from amongnon-circular shapes such as polygonal, teardrop and oval shapes. Thedimple diameter, although not subject to any particular limitation, ispreferably set in a range of from 0.5 to 6 mm. The dimple depth,although likewise not subject to any particular limitation, ispreferably set in a range of from 0.05 to 0.4 mm.

The surface coverage by dimples on the surface of the ball is notsubject to any particular limitation. However, from the standpoint ofthe aerodynamic properties, this value is set to preferably at least70%, more preferably at least 75%, and even more preferably at least80%. By using the mold of the invention, balls having a high surfacecoverage can easily be manufactured.

Although preferred embodiments of the invention have been describedabove in conjunction with the diagrams, the golf ball mold of theinvention is not limited by the diagrams and the above embodiments andmay be suitably modified within the spirit and scope of the presentinvention. That is, the shape of the parting surface of the mold and thenumber of parts into which the mold splits, and the number andpositioning of the support pins specified in the invention may be variedwithin a range that does not depart from the spirit and scope of theinvention. For example, in the mold shown in FIG. 1, the support pins 4provided in the upper mold half 2 a and the lower mold half 2 b need notnecessarily be of identical shape, and may be given differing shapesaccording to, for example, the dimple design. By way of illustration,one could, for instance, adopt a construction in which the upper moldhalf 2 a is provided with the support pin shown in FIGS. 2 and 3 and thelower mold half 2 b is provided with the support pin shown in FIG. 4. Inaddition, known pins and the like may be added, where necessary.

As explained above, the golf ball mold of the present invention, bybeing provided with a support pin having a shape which satisfies certainconditions, is able to stably hold the center sphere at the center ofthe cavity. Hence, eccentricity does not arise, enabling a golf ballhaving a uniform structure to be obtained. In addition, the venting ofgases near the poles when the cover-forming material is injected intothe cavity is good, as a result of which appearance defects do notarise. Moreover, because irregular flash caused by the deflection andshifting of support pins, which has been a concern in conventionalmolds, does not occur, good molded articles can be easily and reliablyobtained, contributing to enhanced golf ball productivity. Also, theshape of the support pin used in the inventive mold is not subject toany dimple design constraints, enabling the degree of freedom in dimpledesign and mold design to be greatly enhanced. Finally, the inventivemold also provides cost advantages in that there is no need for theseparate fabrication of the gas-venting pins used in the large-diametersupport pins having a plurality of dimple-forming protrusions on the endface which have hitherto been described in the art.

The invention claimed is:
 1. The method of manufacturing a golf ball ofusing a golf ball mold comprising a mold body configured as a pluralityof mold parts which have at least a parting surface that defines aparting line at a golf ball equator and removably mate to form a cavityhaving an inner wall with a plurality of dimple-forming protrusionsthereon, and a support pin which has an end face with a plurality ofdimple-forming protrusions thereon and is extendable into andretractable from the cavity, the support pin extending into the cavityto support a center sphere and, when in a retracted state, the end facethereof defining a portion of the inner wall of the cavity, wherein theend face of the support pin includes a pole of the cavity and has aperipheral edge which intersects a parallel of latitude at 10 degreesfrom the pole, comprising the steps of, molding a cover by placing acenter sphere in the mold cavity formed by removably mating theplurality of mold parts which have at least a parting surface thatdefines a parting line at a golf ball equator, and supporting the centersphere with the support pin provided in the mold, then injecting acover-forming material between the center sphere and the cavity innerwall while at the same time retracting the support pin.
 2. The method ofmanufacturing a golf ball of claim 1, wherein the end face of thesupport pin has three or more dimple-forming protrusions thereon.
 3. Themethod of manufacturing a golf ball of claim 2, wherein the end face ofthe support pin has four or more dimple-forming protrusions thereon. 4.The method of manufacturing a golf ball of claim 1, wherein theperipheral edge of the end face on the support pin intersects a parallelof latitude at 8 degrees from the pole.